During normal use, the airflow through a vacuum cleaner can be disrupted. Such disruptions may be caused by blockages or a narrowing of the point of entry of the airflow into the vacuum cleaner, i.e. the cleaner head, tool or wand. However, the airflow may also be disrupted by blockages within the vacuum cleaner such as blockages in the filters or a blockage in a stage of separation. These disruptions result in a reduced flow rate of air through the vacuum cleaner and also a lowering of pressure within the vacuum cleaner.
Typically, the airflow is used to cool the electric motor housed within the vacuum cleaner. Thus, one problem often associated with a reduction of airflow caused by a disruption is that the electric motor of the vacuum cleaner can over heat and become damaged. To avoid this problem, vacuum cleaners may be fitted with a bleed valve that is configured to open when a blockage occurs. Generally, bleed valves are actuated when the pressure within the vacuum cleaner drops below a certain level. Once the bleed valve has opened, air is bled from outside the vacuum into the airflow path so that a minimum airflow to cool the motor is maintained. Ideally, the bleed valve is placed at a position that is as close to the motor as possible to allow for rapid cooling of the motor if necessary.